The long-term objectives of this project are: (1) to determine the pathologic physiology of the menstrual disorders now encountered with increasing frequency in women athletes (delayed menarche, secondary oligo-amenorrhea, infertility attributable to inadequacy of the luteal phase, and dysfunctional uterine bleeding). (2) To utilize such knowledge to devise therapy that will restore menstrual cyclicity in individuals continuing to exercise. At least three hormones with potentially anti-reproductive effects are now known to increase during exercise: melatonin, B-endorphin and prolactin. Accordingly, pharmacologic blocking drugs are being employed in an attempt to delineate the metabolic pathways activated by the stimulus of exercise.